Implantable infusion device with multiple controllable fluid outlets

ABSTRACT

An implantable infusion system includes at least two controllable fluid transfer devices that may be used to transfer different fluid flows to the same or different body sites.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/420,641, now U.S. Pat. No. 8,002,747. filed May 26, 2006, whichclaims the benefit of and priority to previously filed U.S. ProvisionalPatent Application Ser. No. 60/685,126, filed May 26, 2005, which isentitled “Implantable Infusion Device With Multiple ControllableOutlets,” both of which are incorporated herein by reference in theirentirety.

FIELD OF THE INVENTIONS

The present inventions relate generally to implantable infusion devices.

BACKGROUND OF THE INVENTIONS

Implantable infusion devices typically include a housing containing amedication reservoir which can be filled transcutaneously by ahypodermic needle penetrating a fill port septum. The medicationreservoir is generally coupled via an internal flow path to a deviceoutlet port for delivering medication through a catheter to a patientbody site. Typical infusion devices also include a controller and afluid transfer mechanism, such as a pump or a valve, for moving themedication from the reservoir through the internal flow path to thedevice's outlet port. The use of such implantable infusion devices hasbeen well established in pain management, and therapies such as diabetescontrol, where a single medication is delivered to a single body site.

In other therapies, it is desirable to deliver the same medication totwo different body sites, such as cisplatinum to the ovaries for ovariancancer, either at the same rate or at different rates. In yet othertherapies, there is a need to deliver two or more distinct medicationsto different body sites or to the same site independently. For example,with some pain management protocols, it is desirable to deliver morphineand clonidine to a patient's intrathecal site. In certain cancertherapies, it may be desirable to deliver multiple medications tomultiple sites. As a further example, in diabetes therapy, insulin andglucogon may be administered sequentially to lower or to raise bloodsugar respectively.

SUMMARY OF THE INVENTIONS

An implantable infusion device in accordance with one of the presentinventions includes a medication reservoir and at least two controllablefluid transfer devices for respectively transferring first and secondfluid flows to the same or different body sites. Each fluid transferdevice, such as a pump mechanism or a valve mechanism, includes an inletthat may be coupled to a reservoir and an outlet that may be coupled toa catheter for delivering a measured flow to a body site. Such aninfusion device may be used to, for example, deliver a single medicationunder different protocols to a single body site, deliver a singlemedication to multiple body sites, deliver multiple medications tomultiple body sites, deliver multiple medications to a single body site,simultaneously deliver multiple medications at different rates, and/ordeliver one medication at a constant rate and another medication at avariable rate.

An implantable infusion device in accordance with one of the presentinventions includes a medication reservoir with two or morecompartments. Adjacent compartments, which may be used to storedifferent fluids for delivery to the same or different body sites, areseparated by a pressure transmissive partition so that they experiencethe same pressure. There are a variety of advantages to such a device.For example, the use of a common reservoir with two or more compartmentssaves space. Insuring that the reservoirs remain at equal pressuresobviates safety concerns that can be associated with variations inpressure from one compartment to the other. The use of a pressuretransmissive partition also simplifies the overall design of theinfusion device because. More specifically, by maintaining one ofcompartments at the desired pressure, the infusion device will actuallymaintain all of the compartments at the desired pressure.

An implantable infusion device in accordance with one of the presentinventions includes multiple fluid transfer devices that are actuated bya common actuator. Such a device is particularly advantageous because itgreatly reduces the amount of space within the device that must bededicated to the actuation of the fluid transfer devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of an implantable infusion device inaccordance with one embodiment of a present invention.

FIG. 1B is a block diagram of an implantable infusion device inaccordance with one embodiment of a present invention.

FIG. 2 is a block diagram of an implantable infusion device inaccordance with one embodiment of a present invention.

FIG. 3 is a schematic plan view of an implantable infusion device inaccordance with one embodiment of a present invention.

FIG. 4A is a schematic sectional view taken substantially along plane4A-4A in FIG. 3.

FIG. 4B is a schematic sectional view similar to FIG. 4A with analternate reservoir configuration.

FIG. 4C is a schematic partial sectional view similar to FIG. 4A with ananother alternate reservoir configuration.

FIG. 5 is a schematic diagram of a pump head in accordance oneembodiment of a present invention in a fluid intake position.

FIG. 6 is a schematic diagram of a pump head in accordance oneembodiment of a present invention in a discharge position.

FIG. 7 is a schematic diagram of a pair of fluid transfer devices with acommon actuator in accordance one embodiment of a present invention.

FIG. 8 is a schematic diagram of a portion of a common actuator inaccordance one embodiment of a present invention.

FIG. 9 is a schematic diagram of a portion of the common actuatorillustrated in FIG. 8 in an actuation mode.

FIG. 10 is a schematic side view of a portion of an infusion device inaccordance with one embodiment of a present invention.

DETAILED DESCRIPTION

As illustrated for example in FIG. 1A, an implantable infusion device 20in accordance with one embodiment of a present invention includes anouter shell 22 enveloping an interior volume 24. A fluid reservoir 26,which is defined within the internal volume 24, has a fill port 28opening through the outer shell 22. Fluid medication is supplied throughthe fill port 28 (e.g., via a hypodermic needle) to the reservoir 26 forstorage. The fluid reservoir 26 in the illustrated embodiment suppliestwo separate fluid transfer devices. More specifically, the fluidreservoir 26 includes a discharge port 30 that is coupled to a firstfluid transfer path 31 including a first fluid transfer device 32. Thedischarge port 30 is also coupled to a second fluid transfer path 34including a second fluid transfer device 35. The first fluid transferdevice 32 defines an inlet 36 and an outlet 37. Similarly, the secondfluid transfer device 35 defines an inlet 38 and an outlet 39. Theoutlets 37 and 39 open through the outer shell 22 and are adapted tocommunicate with respective catheters for delivering medication from thereservoir 26 to the same or different body sites.

The exemplary fluid transfer devices 32 and 35 are controllable devices,such as selectively actuatable pumps and/or valve mechanisms, which canbe independently operated by a common controller 44, such as amicroprocessor, in accordance with different stored medication profiles,or protocols, that are accessible by the common controller. Each suchprofile can, for example, define delivery start times, deliverydurations, delivery rates and other parameters. Thus, the independentoperation of two or more fluid transfer devices allows the implantableinfusion device 20 (as well as those discussed below) to, for example,deliver a single medication under different protocols to a single bodysite, deliver a single medication to multiple body sites, delivermultiple medications to multiple body sites, deliver multiplemedications to a single body site, simultaneously deliver multiplemedications at different rates, and/or deliver one medication at aconstant rate and another medication at a variable rate, typically inaccordance with a stored profile. The fluid transfer paths 31 and 34 canadditionally include various functional components, such as a pressureregulator and/or sensor, to promote patient safety and device efficacy,as is discussed in detail below in the context of the embodimentillustrated in FIG. 2.

As illustrated for example in FIG. 1B, an implantable infusion device 50in accordance with one embodiment of a present invention includes areservoir 52 having an interior partition 54 forming first and secondcompartments 56 and 58 which can store different first and secondmedications. Compartments 56 and 58 include respective fill ports 60 and62 which open through the device shell 63, and through which medicationscan be supplied to fill the compartments. The compartments 56 and 58 arealso respectively provided with discharge ports 64 and 65, which arecoupled to respective fluid transfer paths 66 and 67. The fluid transferpaths 66 and 67 include the inlets 68 and 70 of fluid transfer devices72 and 74. The fluid transfer devices 72 and 74 also include outlets 76and 78 that are adapted to communicate through the device shell 63 withrespective catheters for delivering the first and second medications tothe same or different body sites. As is discussed below with referenceto FIG. 2, the fluid transfer paths 66 and 67 may also include variousfunctional components that promote patient safety and device efficacy.The fluid transfer devices 72 and 74 are controlled by a controller 80to produce independent medication flows from outlets 76 and 78, whereeach such flow conforms to a stored delivery profile accessed by thecontroller.

One example of a suitable fluid transfer device is a pump mechanism witha fluid chamber and a pump element mounted for movement between anintake position for drawing fluid from the reservoir into the fluidchamber, and a discharge position for discharging fluid from the chamberto an outlet. The pump element can, for example, comprise a pistonmounted for movement by a controlled actuator. Examples of piston-basedpumps are discussed below. It should be noted, however, thatpiston-based pumps in accordance with the present inventions are notlimited to such examples, and that embodiments of the inventions mayinclude pumps that are not piston-based.

Turning to FIG. 2, an implantable infusion device 100 in accordance withone embodiment of a present invention includes a reservoir 119 having aninterior partition 120 forming first and second compartments 122 and 124which can store different first and second medications. Compartments 122and 124 include respective fill ports 126 and 128, which open throughthe device shell 102 and through which medications can be supplied tofill the compartments. The compartments 122 and 124 are alsorespectively provided with discharge ports 131 and 133, which arecoupled to respective fluid transfer paths 144 and 160. The fluidtransfer paths 144 and 160 include the inlets 143 and 158 of fluid pumps140 and 142. The fluid pumps 140 and 142 also include outlets 147 and164 that are adapted to communicate through the device shell 102 withrespective catheters C1 and C2 for delivering the first and secondmedications to the same or different body sites. The exemplary fluidtransfer paths 144 and 160 also include respective pressure regulators146 and 162 which prevent overpressurization in the reservoir fromimpacting the pumps or downstream fluid flow. Respective pressuresensors 152 and 170 are also provided for monitoring pressure to, forexample, detect catheter blockages or leaks. The fluid pumps 140 and 142are controlled by a controller 80 to produce independent medicationflows from outlets 150 and 168 via fluid passageways 148 and 166, whereeach such flow conforms to a stored delivery profile accessed by thecontroller.

FIGS. 3 and 4A schematically depict a structural configuration of anexemplary implantable infusion device 100, shown in block diagram formin FIG. 2, that can produce first and second independently controllablemedication outflows. The device 100 includes a housing or shell 102 witha cup shaped lower member 104 and a detachable cup shaped upper, orcover, member 106. The housing upper member 106 is shown with a dashedline in FIG. 4A and is omitted from FIG. 3 for the sake of clarity. Thehousing lower and upper members 104 and 106 are configured to mate withone another to enclose a volume 108 for accommodating the componentsdepicted in FIG. 2 together with a battery 109 or other suitable powersource. The exemplary housing 102, which is sized for implantation intoa human body, will typically be about 1 to 3 inches long and about 1 to3 inches wide (or 1 to 3 inches in diameter) and less than about 1.5inches thick.

The lower housing member 104 in the exemplary implantable infusiondevice 100 includes an outer wall 110 with a stiff axially extendingring portion 112 and a cross wall portion 114 extending laterally acrossthe bottom edge of the ring portion. The top edge of the ring portion112 supports, and is closed by, a mounting board 116, e.g., a circuitboard. Thus the housing member 104 defines a closed sealed volume 118between the lower surface of mounting board 116 and the interior surfaceof the lower housing cross wall portion 114.

The sealed volume 118 contains an interior partition 120 between a firstreservoir compartment 122 and a second reservoir compartment 124. Thesecompartments are intended to be suitably sealed so that they canrespectively accommodate and isolate different first and secondmedications and/or different concentrations of the same medication, asdiscussed in greater detail below.

In the exemplary embodiment illustrated in FIGS. 3 and 4A, first andsecond fill ports 126 and 128 are supported on the mounting board 116.Each fill port includes a self healing septum 130 which is accessiblethrough cover portion 106 for piercing by a hypodermic needle. The firstfill port 126 communicates via passageway 132 with the first reservoircompartment 122. Similarly, the second fill port 128 communicates viapassageway 134 with the second reservoir compartment 124.

As illustrated for example in FIG. 3, first and second fluid transferdevices, such as pump heads 140 and 142 with an electromagnetic actuator141 mounted on the board 116 between the pump heads, may be provided. Inthe illustrated embodiment, the fluid inlet 143 (FIG. 2) of pump head140 is coupled via a fluid passageway 144, which may include a pressureregulator 146, to the interior of the first compartment 122. The fluidoutlet 147 (FIG. 2) of pump head 140 is coupled via a fluid passageway148 to a first device outlet port 150 adapted for coupling to a firstcatheter. The fluid passageway 148 may include a pressure sensor 152. Inoperation, actuation of the pump head 140 transfers fluid from reservoircompartment 122 past pressure regulator 146 and pressure sensor 152 todevice outlet port 150. Port 150 is preferably configured for couplingto catheter C1 for delivery to an internal body site.

Similarly, the fluid inlet 158 (see FIG. 2) of pump head 142 is coupledvia a fluid passageway 160, which may include a pressure regulator 162,to the interior of the second reservoir compartment 124. The fluidoutlet 164 (see FIG. 2) of pump head 142 is coupled via a fluidpassageway 166 to a second device outlet port 168 adapted for couplingto a second catheter. The fluid passageway 166 may include a pressuresensor 170. Actuation of the pump head 142 acts to transfer fluid fromreservoir compartment 124 to device outlet port 168, through catheterC2, and to a body site.

Although the embodiment illustrated in FIGS. 3 and 4A includes pumpheads 140 and 142, which enable fluid to be transferred from a reservoircompartment held at ambient or negative pressure, other types of fluidtransfer devices may be employed. For example, if the reservoircompartments are held at a positive pressure, then the fluid transferdevices could comprise controlled valves. The prior art shows varioustypes of infusion devices using positive pressure and negative pressurereservoirs for medication delivery. The positive and negative pressuresare typically produced by suitable propellants, such as biphasicpropellants.

In one exemplary embodiment, a negatively biased ambient pressurereservoir of the type generally described in International ApplicationWO 2005/002642, published 13 Jan. 2005, may be employed. The ‘642application describes an infusion device in which a medication reservoirhas a movable wall which is exposed to ambient pressure. The reservoiris configured with a bias device, such as a spring, for exerting a forceto produce a resultant interior pressure which is always negative withrespect to the ambient pressure.

Such a negatively biased ambient pressure is achieved in the embodimentillustrated in FIGS. 3 and 4A by forming the lower housing cross wallportion 114 of a flexible spring material biased to bow outwardly. Theouter surface of cross portion 114 is exposed to a positive ambientpressure F_(A) which acts in a direction tending to collapse the crossportion 114. The inherent spring bias force F_(B) of the cross portion114 acts in a direction opposite to the ambient force F_(A) to producean interior pressure in compartment 124 equal to:P _(C)=(F _(A) −F _(B))/Area

The exemplary partition 120 illustrated in FIGS. 3 and 4A is formed of apressure transmissive material and, accordingly, is a pressuretransmissive partition. As a consequence, the interior pressure incompartment 122 will equal the interior pressure in compartment 124,which will be negative with respect to ambient pressure acting againstthe exterior surface of cross portion 114. In other words, the partition120 performs the function of equalizing the pressure within thecompartments 122 and 124. The exemplary partition 120 has a wavybellows-like shape, or some other non-linear shape, that allows thepartition to adjust in size in response to volumetric changes within thecompartments 122 and 124 in such a manner that the pressure transmissivematerial is not itself substantially stretched.

With respect to materials, examples of suitable pressure transmissivematerials include flexible impermeable polymeric films, i.e. flexiblefilms that do not diffuse solutes or liquids. Specific examples includepolyvinylidene film, polyvinylidene fluoride (PVDF) film, polyvinylidenechloride (PVDC) film, polytetrafluoroethylene film such as Teflon® film,high density polyethylene film, and fluoropolymer film such as Halar®film. The films will typically be about 0.002 inch thick, but the actualthickness will depend on the material employed and the intendedapplication.

An alternative reservoir configuration is illustrated in FIG. 4B. Here,the reservoir includes three compartments. A first reservoir compartment122 is separated from a second reservoir compartment 124 by a firstpressure transmissive partition 120, and a third reservoir compartment125 is separated from the second reservoir compartment 124 by a secondpressure transmissive partition 121. It should be appreciated that thereservoir can be configured with still additional compartments to suitthe intended application. Moreover, it should be understood that sincethe multiple compartments are exposed to the same pressure, the pressuresource, e.g., propellant or ambient pressure, can be associated with anyone of the compartments.

As noted above, positive and negative reservoir pressures may beproduced by a suitable propellant. One example of an implantableinfusion device with a propellant based pressurization arrangement isgenerally represented by reference numeral 100′ in FIG. 4C. Theimplantable infusion device 100′ is substantially identical to theimplantable infusion device 100 illustrated in FIGS. 3 and 4A andsimilar elements are represented by similar reference numerals. Here,however, the lower member 104′ of the shell 102′ does not include theaforementioned flexible cross-wall portion. Instead, an reservoirenclosure 111 with titanium bellows is positioned within the sealedvolume 118, and a pressure transmissive partition 120 is positionedwithin the reservoir enclosure. The pressure transmissive partition 120divides the reservoir within the reservoir enclosure 111 into a firstreservoir compartment 122 and a second compartment 124. The remainder ofthe sealed volume 118 is occupied by propellant P, which may be used toexert positive or negative pressure on the reservoir enclosure 111. Heretoo, the pressure within the first and second compartments 122 and 124will be equalized by the pressure transmissive partition 120.

Turning to FIGS. 5 and 6, an exemplary pump head 180 has a fluid intake(rest) position and a fluid discharge (actuated) position. The pump head180 may, for example, be used as the pump head 140 and/or the pump head142 described above with reference to FIGS. 3 and 4. The pump head 180may be actuated by a variety of different actuators. One such actuatoris the common actuator 250, which is discussed in detail below withreference to FIG. 7 and includes the hammer 220 illustrated in FIGS. 5and 6. Alternatively, in those instances where two or more pump headsare employed, each pump head may be paired with its own individualactuator, if desired.

The exemplary pump head 180 includes a block 182 defining a bore 183extending inwardly from block end face 184. The bore 183 includes aninlet chamber 185 leading into a piston channel 186. A fluid intake port187 opens into piston channel 186 from a passageway 190 coupled to afluid source, e.g., reservoir compartment 122. Channel 186 is configuredto open into a reduced channel outlet port 192. A piston 194 is mountedin channel 186 for reciprocal linear movement, i.e. from the quiescentintake (rest) position illustrated in FIG. 5 to the actuated dischargeposition illustrated in FIG. 6, and back to the intake (rest) position.The clearance space 195 between the piston 194 and the piston channel186 should be minimized to insure efficient and consistent fluid volumedischarge per stroke. The piston 194 has a strike end 198 (at the rightas viewed in FIG. 5) and a pressure end or face 200 (at the left). Thestrike end 198 in the illustrated embodiment includes a reduced diameterstrike pin portion 202 extending from a greater diameter energy transferportion 203. The portions 202 and 203 are retained by a spring diaphragm210 which seals the bore 183. The piston 194 has a flange 204 carrying aball portion 205 aligned with energy transfer portion 203. A returnspring 208 bears against the left face of flange 204 urging it to theright to engage portions 203 and 205. The spring diaphragm 210 assistsin centering the piston body 206 in channel 186 and establishing thequiescent intake (rest) position of the piston 194.

A pump chamber 213 is defined between the piston pressure face 200 andthe channel outlet port 192. An elastomeric check valve element 212,normally urged closed by spring 214, is mounted between channel outletport 192 and the pump head outlet 216.

In one exemplary implementation of the pump head 180, the pump chambervolume is approximately 0.25 microliters. When actuated by the hammer220 axially striking the free end 217 of the strike pin portion 202,piston pressure face 200 moves approximately 0.20 millimeters withinapproximately 2 milliseconds or less to force a fluid volume (strokevolume) of approximately 0.25 microliters out through port 192 to thepump head outlet 216. To optimize the transfer of energy from hammer 220to pin portion 202, it is preferable to provide a small gap 231 betweenthe hammer 220 and the strike pin portion 202 to build up kineticenergy. The gap 231 can be adjusted by including a stroke adjustmentshim 222 which can be variably positioned along the portion 202 forengaging stop surface 224.

More particularly, assume that the pump head 180 is initially in thequiescent intake (rest) position depicted in FIG. 5. In this position,fluid from the reservoir compartment 122 fills passageway 190 and, viaport 187, the bore 183 including inlet chamber 185, the clearance space195 surrounding piston 194, and the pump chamber 213. When the pump head180 is actuated such that hammer 220 drives piston 194 from the positionillustrated in FIG. 5 to the position illustrated in FIG. 6, thepressure face 200 forces pump chamber fluid through channel outlet port192 and past valve element 212 to pump head outlet 216. The clearancespace 195 is minimized (e.g., approximately 5.0 microns or less) so thatmost of the fluid in the pump chamber 213 is forced out through outletport 192 with only a small portion moving back though the clearancespace 195 to passageway 190 and the reservoir compartment 122.

As should be appreciated, the axial hammer force required to actuate thepump head, i.e. to move the piston 194 from the position illustrated inFIG. 5 to the position illustrated in FIG. 6, must transfer sufficientenergy to:

-   -   1) Deflect diaphragm 210,    -   2) Compress return spring 208,    -   3) Compress valve spring 214, and    -   4) Overcome head pressure at the pump head outlet 216 which can,        for example, include some degree of occlusion in a downstream        catheter.        Also, the return spring 208 and diaphragm 210 must provide a        sufficient axial restoration force to return the piston 194 from        the discharge (actuated) position illustrated in FIG. 6 to the        intake (rest) position illustrated in FIG. 5 once the hammer        force has terminated.

The axial force applied to strike pin 202 to actuate the pump head 180can be produced by various mechanisms. One example of a such a mechanismis a common actuator 250 illustrated in FIG. 7. The common actuator 250,which includes the aforementioned hammer 220, may be used to actuate apair of pump heads 180.

As used herein, a “common actuator” is a single device that can beassociated with a plurality of pump heads or other fluid transferdevices and actuated in more than one actuation mode to independentlydrive (or not drive) each of the fluid transfer devices. Morespecifically, a common actuator that is used in combination with a firstand second fluid transfer devices may have a first actuation mode thatactuates the first fluid transfer device to discharge fluid while thesecond fluid transfer device remains unactuated, a second actuation modethat causes the second fluid transfer device to discharge fluid whilethe first fluid transfer device remains unactuated, and a neutral mode.The term “neutral mode” describes a state where common actuator (or aportion of the common actuator) is in a position or condition thatresults in both fluid transfer devices remaining unactuated. In theexemplary context of the pump heads, a common actuator that is used incombination with first and second pump heads may have a first actuationmode that drives the first pump head to discharge fluid while the secondpump head remains in the intake position, a second actuation mode thatdrives the second pump head to discharge fluid while the first pump headremains in the intake position, and a neutral mode that allows both pumpheads to remain in their respective intake positions. An actuation cycleoccurs when the common actuator transitions from the neutral mode to thefirst (or second) actuation mode and back to the neutral mode. Dependingon the desired actuation rate, the common actuator may remain in theneutral mode at the end of the actuation cycle for a predeterminedperiod before beginning the next actuation cycle. Alternatively, at theend of an action cycle, the common actuator will immediately begin thenext actuation cycle.

A common actuator may be used to drive different pump heads (or otherfluid transfer devices) at the same rate or at different rates. Withrespect to driving the pump heads at the same rate, this may beaccomplished by simply alternating between the first and second modes,with or without pauses in the neutral mode between each actuation cycleor between some combination of actuation cycles. Different pump headdriving rates may be accomplished by actuating one pump head morefrequently than the other. For example, the common actuator could beoperated such that the first actuation mode occurs twice for eachoccurrence of the second actuation mode. Another exemplary actuationregimen is useful in those instances where one medication is dispensedat a regular interval (or constant rate) and another medication isdispensed at a variable rate, e.g. in response to a predetermined bodilycondition or patient request. Here, the common actuator could beactuated in the first actuation mode at the regular interval and onlyactuated in the second actuation mode in response to the predeterminedbodily condition or patient request.

Referring again to FIG. 7, and although common actuators are not solimited, one example of a common actuator that may be used to actuatefirst and second pump heads 180 a and 180 b, which are identical to pumphead 180 and shown here in simplified form, is the common actuator 250.In the first actuation mode, the hammer 220 is linearly driven in afirst direction to actuate the first pump head 180 a and, in the secondactuation mode, the hammer is linearly driven in a second direction toactuate the second pump head 180 b. The second pump head 180 b willremain in the intake position during the first actuation mode, while thefirst pump head 180 b will remain in the intake position during thesecond actuation mode. The common actuator 250 also has a neutral mode,where neither of the pump heads 180 a and 180 b are actuated. The commonactuator 250 is shown in the neutral mode in FIG. 7.

The hammer 220 in the illustrated embodiment is a rod of magneticmaterial (i.e. an armature) that is suspended by spring mounts 232. Thehammer 220 also extends axially through a fixedly positioned coilwinding 234. In the first actuation mode, current is driven through thecoil winding 234 in one direction and the resulting electromagneticforce propels the hammer 220 in the first direction against the strikepin 202 of pump head 180 a. The spring mounts 232 will return the hammer220 to the neutral position when current flow ends (e.g. about 20-100milliseconds after it begins in some embodiments), thereby completingthe actuation cycle. Current is driven through the coil winding 234 inthe opposite direction in the second actuation mode. The resultingelectromagnetic force propels the hammer 220 in the second directionagainst the strike pin 202 of pump head 180 b. Here too, the springmounts 232 will return the hammer 220 to the neutral position whencurrent flow ends. The current driven through the coil winding 234 maybe controlled by a suitable controller such as, for example, thecontroller 44 (FIG. 1) or the controller 80 (FIG. 2).

The common actuator illustrated in FIG. 7 is merely one example of acommon actuator that may be used to selectively drive two or more fluidtransfer devices. With respect to those which employ electromagneticforce to selectively drive a hammer, one alternative is a moving coilactuator. Here, a magnet is held in a fixed position and a coil movesrelative thereto. A hammer is carried by the coil, or individual hammersmay be carried at opposite ends of the coil, for movement with the coil.Another alternative is illustrated in FIGS. 8 and 9. Here, instead ofthe aforementioned spring mounts 232, the common actuator 250′ (which isotherwise identical to actuator 250), includes resilient membranes 233(only one shown in FIGS. 8 and 9) or other resilient devices that arepositioned over the longitudinal ends of the hammer 220. The resilientmembranes 233 perform the same functions as the spring mounts 232. Morespecifically, when the current induced electromagnetic force that drivesthe hammer 220 from the position illustrated in FIG. 8 to the strikeposition illustrated in FIG. 9, and stretches the membrane 233 isremoved, the membrane will drive the hammer back to the positionillustrated in FIG. 8.

Another exemplary common actuator that may be used to selectivelyactuate first and second fluid transfer devices is generally representedby reference numeral 252 in FIG. 10. Although the common actuator 252may be used in combination with a variety of fluid transfer devices,pump heads 180 a and 180 b are shown for purposes of illustration. Theactuator 252, which is in its neutral mode orientation in FIG. 10,includes first and second piezoceramic disks 254 and 256 that arecarried by a flexible diaphragm 258. The piezoceramic disks 254 and 256carry hammers 260 and 262. In the first actuation mode, a voltage isapplied across the piezoceramic disk 254, thereby causing the disk tobend in the first direction (i.e. to the left in FIG. 10). The hammer260 will, in turn, strike the strike pin 202 of the pump head 180 a anddrive the associated piston to the discharge position. The piezoceramicdisk 254, as well the remainder of the common actuator 252, will returnto the neutral mode illustrated in FIG. 10 when the voltage is removed.Similarly, in the second actuation mode, a voltage is applied across thepiezoceramic disk 256, thereby causing the a disk to bend in the seconddirection (i.e. to the right in FIG. 10). The hammer 262 will, in turn,strike the strike pin 202 of the pump head 180 b and drive theassociated piston to the discharge position.

Other piezo-type common actuators may also be employed. By way ofexample, a single piezoceramic disk that bends in opposite directionsbased on the polarity of the applied voltage, and has unbent neutralstate, may be carried on the flexible diaphragm 258 in place of thedisks illustrated in FIG. 10. Cantilevered piezo elements, which areanother alternative, eliminate the need for the flexible diaphragm.Additionally, in any piezo-type common actuator, the hammer(s) may beeliminated so that a piezoceramic element strikes the strike pin 202 orthe corresponding portion of some other fluid transfer device.Piezo-type common actuators may also be employed in those instanceswhere the fluid transfer devices are microelectromechanical system(MEMS) based pumps or valves.

Common actuators that may be used to selectively actuate a plurality offluid transfer devices are not limited to those which move linearly backand forth. For example, rotary cam actuators that have, for example,left, right and neutral positions may be employed. An actuator thatrelies on the heat triggered expansion of a gas, such as air, may alsobe used as common actuator for selectively actuating two or more fluidtransfer devices.

Although the inventions disclosed herein have been described in terms ofthe preferred embodiments above, numerous modifications and/or additionsto the above-described preferred embodiments would be readily apparentto one skilled in the art. By way of example, but not limitation, insome applications it may be desirable to utilize a single pump mechanismand an appropriate valve arrangement to produce controlled fluid flowsfrom multiple reservoir compartments. The inventions also include anycombination of the elements from the various species and embodimentsdisclosed in the specification that are not already described. It isintended that the scope of the present inventions extend to all suchmodifications and/or additions and that the scope of the presentinventions is limited solely by the claims set forth below.

We claim:
 1. An infusion device configured for implantation in apatient's body, the infusion device comprising: a housing; a pressuresource associated with the housing; a reservoir in the housing includingat least first and second reservoir compartments, the first and secondreservoir compartments being positioned relative to one another andrelative to the pressure source such that the pressure source actsdirectly on the first reservoir and the first reservoir separates thepressure source from the second reservoir; a pressure transmissiveinterior partition between the first and second reservoir compartmentsconfigured to equalize pressure within the first and second reservoircompartments; a first fluid transfer device operably connected to thefirst reservoir compartment and to a first fluid outlet; a second fluidtransfer device operably connected to the second reservoir compartmentand to a second fluid outlet; and a controller that controls at leastone of the first and second fluid transfer devices.
 2. The device ofclaim 1 wherein the pressure source comprises a propellant that producesa consistent positive pressure.
 3. The device of claim 1 wherein thepressure source comprises a propellant that produces a consistentnegative pressure.
 4. The device of claim 1 wherein the pressure sourcecomprises a pressure transmissive outer wall configured to negativelybias the pressure in the compartments relative to the ambient pressure.5. The device of claim 1 further comprising a third reservoircompartment; and a pressure transmissive interior partition between thesecond and third reservoir compartments configured to equalize pressurewithin the second and third reservoir compartments.
 6. The device ofclaim 1, wherein the pressure transmissive interior partition comprisesa flexible polymeric membrane.
 7. The device of claim 1, wherein thepressure transmissive interior partition has a wavy shape.
 8. The deviceof claim 1, wherein the first fluid transfer device comprises a pump. 9.The device of claim 1, wherein the first fluid transfer device comprisesa first pump; and the second fluid transfer device comprises a secondpump.
 10. The device of claim 1, wherein the first fluid transfer devicecomprises a valve.
 11. The device of claim 1, wherein the first fluidtransfer device comprises a first valve; and the second fluid transferdevice comprises a second valve.
 12. The device of claim 1, wherein thefirst fluid outlet comprises a first catheter port; and the second fluidoutlet comprises a second catheter port.
 13. The device of claim 12,wherein the first and second catheter ports are located in spacedrelation to one another.
 14. The device of claim 1 further comprising: afirst drug in the first reservoir compartment; and a second drug in thesecond reservoir compartment.
 15. The device of claim 1 wherein thepressure source comprises a resilient member having an exterior surfacethat is exposed to ambient pressure and an interior surface; theresilient member interior surface and the pressure transmissive interiorpartition define the first reservoir compartment; the resilient memberis self-biased away from the first reservoir compartment with enoughforce to create a pressure within the first reservoir compartment thatis negative with respect to the ambient pressure; and the secondreservoir compartment is completely separated from the resilient memberby the pressure transmissive interior partition.
 16. The device of claimwherein the second reservoir compartment is located within the firstreservoir compartment.
 17. The device of claim 1 further comprising afirst fluid passageway that connects the first reservoir compartment tothe first fluid transfer device; and a second fluid passageway thatconnects the second reservoir compartment to the second fluid transferdevice.
 18. The device of claim 1 wherein wherein the pressure source isthe only non-pump pressure source associated with the first and secondreservoir compartments.
 19. An infusion device configured forimplantation in a patient's body, the infusion device comprising: ahousing; a reservoir in the housing including at least first and secondreservoir compartments; a first pump connected to the first drugreservoir compartment by a first passageway and connected to a firstcatheter port; a second pump connected to the second drug reservoircompartment by a second passageway and connected to a second catheterport; means, located between the first and second drug reservoircompartments, for equalizing pressure within the first and second drugreservoir compartments; and a controller that controls at least one ofthe first and second pumps.
 20. The device of claim 19, wherein thefirst and second catheter ports are located in spaced relation to oneanother.
 21. The device of claim 19 further comprising: a first drug inthe first drug reservoir compartment; and a second drug in the drugsecond reservoir compartment.
 22. The device of claim 19 wherein thehousing includes a resilient member having an exterior surface that isexposed to ambient pressure and an interior surface; the resilientmember interior surface and the means for equalizing pressure define thefirst drug reservoir compartment; the resilient member is self-biasedaway from the first drug reservoir compartment with enough force tocreate a pressure within the first drug reservoir compartment that isnegative with respect to the ambient pressure; and the second drugreservoir compartment is completely separated from the resilient memberby the means for equalizing pressure.
 23. The device of claim 19 whereinthe first drug reservoir compartment is directly exposed to a non-pumpsource of negative pressure; and the second drug reservoir compartmentis not directly exposed to a non-pump source of negative pressure.